1. Sensation is the mechanical process by which our sensory receptors respond to stimulation from the environment. Perception is an active process that involves organizing sensations based on experience, expectations, and motivations. 2. The senses of vision, hearing, touch, taste and smell all involve transduction, where stimuli are converted to neural signals. However, the specific transduction processes differ between senses. 3. The relationship between sensation and perception is that sensation provides the raw sensory input and perception involves higher-level cognitive processing to interpret these sensations and give them meaning.

1. SENSATION AND PERCEPTION

2. Sensation & Perception
• How Does Stimulation Become Sensation?
• How Are the Senses Alike? How Are They
Different?
• What Is the Relationship between Sensation
and Perception?

3. How Does Stimulation Become
Sensation?
• Transduction: Changing Stimulation to
Sensation
• Thresholds: The Boundaries of Sensation
Signal Detection Theory

4. Transduction
• Transforming signals into neural impulses.
• Information goes from the senses to the thalamus , then
to the various areas in the brain.

5. Sensory Adaptation
• Decreased
responsiveness to
stimuli due to constant
stimulation.
Do you feel your underwear all day?

6. Cocktail-party phenomenon
• The cocktail party effect
describes the ability to focus
one's listening attention on a
single talker among a mixture of
conversations and background
noises, ignoring other
conversations.
• Form of selective attention.

7. How Are the Senses Alike? How Are
They Different?
• Vision: How the Nervous System Processes Light
• Hearing: If a Tree Falls in the Forest . . . How the
Other Senses Are Like Vision and
• Hearing
Synesthesia: Sensations across the Senses
Energy Senses Chemical Senses

8. Energy v. Chemical senses
Energy Senses Chemical Senses

9. Vision

10. Step One: Gathering Light
The Eye
Light enters through
a narrow opening
Cornea – transparent eye
cover
Iris – muscle; colored
part of the eye
Pupil – opening in the iris
• Sensitive to light and
emotion

11. Step Two: Within the Eye

12. Step Three: Transduction

13. Step Four: In the Brain
• Feature
detectors-
– Hubel and Wiesel
– groups of
neurons in the
visual cortex
respond to
different types of
visual images.

14. Feature Detectors

15. Theories of
color vision:
Explain our
ability to
distinguish
between colors
Trichromatic
theory
•Young-Helmholtz:
three types of
receptors (cones)
all others
variations
Opponent-
process theory
•Hering: three
types of bipolar
receptors
•Supported by
negative
afterimages
Thought to
work together:
•Thricomatic:
Cones
•Opponent-
Process:
Thalamus
Color Vision

16. Trichromatic Theory
Three types of cones:
• Red
• Blue
• Green
• These three types of
cones can make millions
of combinations of
colors.
• Does not explain
afterimages or color
blindness well.

18. Opponent-Process theory
The sensory receptors
come in pairs.
• Red/Green
• Yellow/Blue
• Black/White
• If one color is
stimulated, the
other is inhibited.

19. Plates from a Test for Color Blindness

23. Principles of Visual Perception
• Process used to organize sensory impressions
caused by the light that strikes our eyes
• Sensation is a mechanical process
• Perception is an active process
– Involves experience, expectations and
motivations

24. Perceptual Organization
• Figure – Ground Perception
– Ambiguous, unstable figures, we shift back & forth

25. 1. Visual Perception
• Process used to organize sensory impressions
caused by the light that strikes our eyes
• Sensation is a mechanical process
• Perception is an active process
– Involves experience, expectations and
motivations

26. 1. Visual Perception
• Process used to organize sensory impressions
caused by the light that strikes our eyes
• Sensation is a mechanical process
• Perception is an active process
– Involves experience, expectations and
motivations

27. Gestalt Rules for Perceptual
Organization

28. Perception of Motion
• Visual perception of motion is based on change
of position relative to other objects
• Illusions of movement
– Stroboscopic motion (class discussion, how
do we know that a train moves?)
• Induced Motion:
http://psychlab1.hanover.edu/Classes/Sensati
on/induced/index.html

29. • Binocular Cues
– Retinal disparity
– Convergence
• Monocular cues
Depth Perception

30. Constancy
• Acquired through experience; creates stability
– Size Constancy
– Color Constancy
– Brightness Constancy
– Shape Constancy

32. Faces
• http://www.michaelbach.de/ot/fcs_hollow-
face/index.html

33. Lightness Perception
• http://persci.mit.edu/demos/gaz/main-
frameset.html

34. Turning Tables
• http://www.michaelbach.de/ot/sze_shepardT
ables/index.html

35. Perception and Culture

36. Hearing: Transduction in the Ear

37. Pitch Theories
• Different hairs vibrate
in the cochlea when
they different pitches.
• So some hairs vibrate
when they hear high
and other vibrate
when they hear low
pitches.
Place Theory
• The height of the
wave gives us the
amplitude of the
sound.
• The frequency of the
wave gives us the
pitch if the sound.
Frequency Theory

38. Deafness
• Conduction Deafness
– Something goes wrong with the sound and the vibration on the way
to the cochlea.
• Nerve (sensorineural) Deafness

39. Touch
• Cutaneous Senses:
Receptors located in our
skin.
• Dermatomes

40. • Gate control theory: sensations are mediated
by neural gates in the spinal cord that lalow
them to continue to brain
Pain

41. Taste
• We have bumps on our
tongue called papillae.
• Taste buds are located
on the papillae (they
are actually all over the
mouth).
• Sweet, salty, sour and
bitter.

42. • Primary olfactory cortex
• Orbitofrontal cortex
• Amygdala
Olfaction

43. BODY POSITION SENSES

44. Vestibular Sense
• Tells us where our body
is oriented in space.
• Our sense of balance.
• Located in our
semicircular canals in
our ears.

45. Kinesthetic Sense
• Tells us where our body
parts are.
• Receptors located in our
muscles and joints.

46. What Is the Relationship between
Sensation and Perception?
• Perceptual Processing: Finding Meaning in
Sensation
• Perceptual Ambiguity and Distortion
Theoretical Explanations for Perception Seeing
and Believing

47. Perception
• We see things
• How do our minds make our worlds?

48. Thresholds
Absolute threshold:
• The absolute threshold is
the smallest amount of
stimulus we can detect.
Difference threshold:
• How much does a
stimulus need to change
before we notice the
difference?

49. Weber’s Law

50. Stepping Feet
• http://www.michaelbach.de/ot/mot-
feetLin/index.html